It is useful to know the mass of a vehicle for various purposes. For example, the mass of the vehicle will impact how long it will take the vehicle to stop if a particular braking force is applied. This is particularly important in vehicles such as over-the-road trucks that can perform very differently when fully loaded, partially loaded, or unloaded. The mass of the vehicle is important for purposes of determining the correct amount of power to be provided by an engine under different load conditions. For example, an excessive error with respect to the mass of the vehicle can result in the vehicle either being sluggish or overpowered and not producing desired fuel efficiency. It is not always practical to weigh a loaded, vehicle to determine its actual mass.
It is desirable to provide a convenient and accurate method and arrangement for estimating the mass of a vehicle.
In accordance with an aspect of the invention, a method of estimating vehicle mass (m) comprises determining acceleration of the vehicle over a first period (A1) when a first force (F1) from an engine is applied to wheels of the vehicle, determining acceleration of the vehicle over a second period (A2) when a second force (F2) from the engine is applied to the vehicle wheels, estimating a first value of vehicle mass (m0) from an equation where:m0=dF/dA wherein,dF=F2=F1dA=A2−A1,estimating a second value of vehicle mass (m1) during the first period and a third value of vehicle mass (m2) by approximating values of a first resistance parameter (R1) during the first period and a second resistance parameter (R2) during the second period, wherein:R1={−m0*A1+F1−½*δ*a*Cd*V12}/(m0)R2={−m0*A2+F2−½*δ*a*Cd*V22}/(m0)                wherein:        δ=air density        Cd=coefficient of drag on the vehicle        a=frontal area of vehicle        V1=average vehicle velocity during, the first period        V2=average vehicle velocity during the second period        R1=a first resistance parameter during the first period        R2=a second resistance parameter during the second period,and solving for m1 and m2 via the equations:m1={F1−½*δ*a*Cd*V12}/(A1+R2)m2={F2−½*δ*a*Cd*V22}/(A2+R1),and estimating in using values including at least m0, m1, and m2.        
In accordance with another aspect of the present invention, a vehicle comprising an arrangement for estimating a mass (m) of the vehicle comprises an engine and wheels, the engine being arranged to apply force to the wheels of the vehicle, a speedometer arranged to measure speed of the vehicle and provide a speedometer signal corresponding to the measured speed, and a control unit arranged to receive the speedometer signal and one or more signals from the engine and to calculate force applied to the wheels of the vehicle as a function of the one or more engine signals. The control unit is arranged to determine acceleration of the vehicle over a first period (A1) when a first force (F1) from an engine is applied to wheels of the vehicle, determine acceleration of the vehicle over a second period (A2) when a second force (F2) from the engine is applied to the vehicle wheels, estimate a first value of vehicle mass (m0) from an equation where:m0=dF/dA wherein,dF=F2−F1dA=A2−A1,estimate a second value of vehicle mass (m1) during the first period and a third value, of vehicle mass (m2) by approximating values of a first resistance parameter (R1) during the first period and a second resistance parameter (R2) during the second period, wherein:R1={−m0*A1+F1−½*δ*a*Cd*V12}/(m0)R2={−m0*A2+F2−½*δ*a*Cd*V22}/(m0)                wherein:        δ=air density        Cd=coefficient of drag on the vehicle        a=frontal area of vehicle        V1=average vehicle velocity during the first period        V2=average vehicle velocity during the second period        R1=a first resistance parameter during the first period        R2=a second resistance parameter during the second period, and                    solving for m1 and m2 via the equations:m1={F1−½*δ*a*Cd*V12}/(A1+R2)m2={F2−½*δ*a*Cd*v22}/(A2+R1), andestimate in using values including at least m0, m1, and m2.                        